1. Field of the Invention
The present invention relates to novel substituted indole compounds that are antagonists of alpha V (αv) integrins, for example αvβ3 and αvβ5 integrins, their pharmaceutically acceptable salts, and pharmaceutical compositions thereof.
2. Related Art
Integrins are cell surface glycoprotein receptors which bind extracellular matrix proteins and mediate cell-cell and cell-extracellular matrix interactions (generally referred to as cell adhesion events) (Hynes, R. O., Cell 69:11-25 (1992)). These receptors are composed of noncovalently associated alpha (α) and beta (β) chains which combine to give a variety of heterodimeric proteins with distinct cellular and adhesive specificities (Albeda, S. M., Lab. Invest. 68:4-14 (1993)). Recent studies have implicated integrins in the regulation of cellular adhesion, migration, invasion, proliferation, apoptosis and gene expression (Albeda, S. M., Lab. Invest. 68:4-14 (1993); Juliano, R., Cancer Met. Rev. 13:25-30 (1994); Ruoslahti, E. and Reed, J. C. , Cell 77:477-478 (1994); and Ruoslahti, E. and Giancotti, F. G., Cancer Cells 1:119-126 (1989)).
One member of the integrin family which has been shown to play a significant role in a number of pathological conditions is the integrin αvβ3, or vitronectin receptor (Brooks, P. C., DN&P 10(8):456-461 (1997)). This integrin binds a variety of extracellular matrix components and other ligands, including fibrin, fibrinogen, fibronectin, vitronectin, laminin, thrombospondin, and proteolyzed or denatured collagen (Cheresh, D. A., Cancer Met. Rev. 10:3-10 (1991) and Shattil, S. J., Thromb. Haemost. 74:149-155 (1995)). The two related αv integrins, αvβ5 and αvβ1 (also vitronectin receptors), are more specific and bind vitronectin (αvβ5) or fibronectin and vitronectin (αvβ1) (Horton, M., Int. J. Exp. Pathol. 71:741-759 (1990)). αvβ3 and the other integrins recognize and bind to their ligands through the tripeptide sequence Arg-Gly-Asp (“RGD”) (Cheresh, D. A., Cancer Met. Rev. 10:3-10 (1991) and Shattil, S. J., Thromb. Haemost. 74:149-155 (1995)) found within all the ligands mentioned above.
The αvβ3 integrin has been implicated in a number of pathological processes and conditions, including metastasis and tumor growth, pathological angiogenesis, and restenosis. For example, several studies have clearly implicated αvβ3 in the metastatic cascade (Cheresh, D. A., Cancer Met. Rev. 10:3-10 (1991); Nip, J. et al., J. Clin. Invest. 95:2096-2103 (1995); and Yun, Z., et al., Cancer Res. 56:3101-3111 (1996)). Vertically invasive lesions in melanomas are also commonly associated with high levels of αvβ3, whereas horizontally growing noninvasive lesions have little if any αvβ3 (Albeda, S. M., et al., Cancer Res. 50:6757-6764 (1990)). Moreover, Brooks et al. (in Cell 79:1157-1164 (1994)) have demonstrated that systemic administration of αvβ3 antagonists disrupts ongoing angiogenesis on chick chorioallantoic membrane (“CAM”), leading to the rapid regression of histologically distinct human tumors transplanted onto the CAM. These results indicate that antagonists of αvβ3 may provide a therapeutic approach for the treatment of neoplasia (solid tumor growth).
αvβ3 has also been implicated in angiogenesis, which is the development of new vessels from preexisting vessels, a process that plays a significant role in a variety of normal and pathological biological events. It has been demonstrated that αvβ3 is up-regulated in actively proliferating blood vessels undergoing angiogenesis during wound healing as well as in solid tumor growth. Also, antagonists of αvβ3 have been shown to significantly inhibit angiogenesis induced by cytokines and solid tumor fragments (Brooks, P. C., et al., Science 264:569-571 (1994); Enenstein, J. and Kramer, R. H., J. Invest. Dermatol. 103:381-386 (1994); Gladson, C. L., J. Neuropathol. Exp. Neurol 55:1143-1149 (1996); Okada, Y., et al., Amer. J. Pathol. 149:37-44 (1996); and Brooks, P. C., et al., J. Clin. Invest. 96:1815-1822 (1995)). Such αvβ3 antagonists would be useful for treating conditions that are associated with pathological angiogenesis, such as rheumatoid arthritis, diabetic retinopathy, macular degeneration, and psoriasis (Nicosia, R. F. and Madri, J. A., Amer. J. Pathol. 128:78-90 (1987); Boudreau, N. and Rabinovitch, M., Lab. Invest. 64:187-99 (1991); and Brooks, P. C., Cancer Met. Rev. 15:187-194 (1996)).
There is also evidence that αvβ3 plays a role in neointimal hyperplasia after angioplasty and restenosis. For example, peptide antagonists and monoclonal antibodies directed to both αvβ3 and the platelet receptor αIIbβ3 have been shown to inhibit neointimal hyperplasia in vivo (Choi, E. T., et al., J. Vasc. Surg. 19:125-134 (1994); and Topol, E. J., et al., Lancet 343:881-886 (1994)), and recent clinical trials with a monoclonal antibody directed to both αIIbβ3 and αvβ3 have resulted in significant reduction in restenosis, providing clinical evidence of the therapeutic utility of β3 antagonists (Topol, E. J., et al., Lancet 343:881-886 (1994)).
It has also been reported that αvβ3 is the major integrin on osteoclasts responsible for attachment to bone. Osteoclasts cause bone resorption. When bone resorbing activity exceeds bone forming activity, the result is osteoporosis, a condition which leads to an increased number of bone fractures, incapacitation and increased mortality. Antagonists of αvβ3 have been shown to be potent antagonists of osteoclastic activity both in vitro (Sato, M., et al., J. Cell Biol. 111:1713-1723 (1990)) and in vivo (Fisher, J. E., et al., Endocrinology 132:1411-1413 (1993)).
Lastly, White (in Current Biology 3(9):596-599 (1993)) has reported that adenovirus uses αvβ3 for entering host cells. The αvβ3 integrin appears to be required for endocytosis of the virus particle and may be required for penetration of the viral genome into the host cell cytoplasm. Thus compounds which inhibit αvβ3 could be useful as antiviral agents.
The αvβ5 integrin has been implicated in pathological processes as well. Friedlander et al. have demonstrated that a monoclonal antibody for αvβ5 can inhibit VEGF-induced angiogenesis in rabbit cornea and chick chorioalloantoic membrane, indicating that the αvβ5 integrin plays a role in mediating growth factor-induced angiogenesis (Friedlander, M. C., et al., Science 270:1500-1502 (1995)). Compounds that act as αvβ5 antagonists could be used to inhibit pathological angiogenesis in tissues of the body, including ocular tissue undergoing neovascularization, inflamed tissue, solid tumors, metastases, or tissues undergoing restenosis.
Discovery of the involvement of αvβ3 and αvβ5 in such processes and pathological conditions has led to an interest in these integrins as potential therapeutic targets, as suggested in the preceding paragraphs. A number of specific antagonists of αvβ3 and αvβ5 that can block the activity of these integrins have been developed. One major group of such antagonists includes nonpeptide mimetics and organic-type compounds. For example, a number of organic non-peptidic mimetics have been developed that appear to inhibit tumor cell adhesion to a number of αvβ3 ligands, including vitronectin, fibronectin, and fibrinogen (Greenspoon, N., et al., Biochemistry 32:1001-1008 (1993); Ku, T. W., et al., J. Amer. Chem. Soc. 115:8861-8862 (1993); Hershkoviz, R., et al., Clin. Exp. Immunol. 95:270-276 (1994); and Hardan, L., et al., Int. J. Cancer 55:1023-1028 (1993)).
Additional organic compounds developed specifically as αvβ3 or αvβ5 integrin antagonists or as compounds useful in the treatment of αv-mediated conditions have been described in several recent publications.
For example, U.S. Pat. No. 5,741,796, issued Apr. 21, 1998, discloses pyridyl and naphthyridyl compounds for inhibiting osteoclast-mediated bone resorption.
PCT Published Application WO 97/45137, published Oct. 9, 1997, discloses non-peptide sulfotyrosine derivatives, as well as cyclopeptides, fusion proteins, and monoclonal antibodies, that are useful as antagonists of αvβ3 integrin-mediated angiogenesis.
PCT Published Application WO 97/36859, published Oct. 9, 1997, discloses para-substituted phenylpropanoic acid derivatives of the general formula:                 where A is: or —OCH2—;        Y1 is selected from the group consisting of N—R2, O and S;        Y3 and Z3 are independently selected from the group consisting of H, alkyl, aryl, cycloalkyl and aralkyl, or Y3 and Z3 taken together with C form a carbonyl;        R50 is selected from the group consisting of H, alkyl, aryl, carboxyl derivative and —CONHCH2CO2R53, wherein R53 is H or lower alkyl; and        R51 is selected from the group consisting of H, alkyl, carboxyl derivatives,         wherein R54 is selected from the group consisting of H, alkyl, cycloalkyl, aryl, aralkyl, aralkenyl and aryl substituted by one or more alkyl or halo; and wherein R55 is selected from the group consisting of N-substituted pyrrolidinyl, piperidinyl and morpholinyl.        
The publication also discloses the use of the compounds as αvβ3 integrin antagonists.
PCT Published Application WO 97/06791, published February 1997, discloses methods for inhibition of angiogenesis in tissue using vitronectin αvβ5 antagonists.
More recently, PCT Published Application WO 97/23451, published Jul. 3, 1997, discloses tyrosine derivatives of the general formula: wherein                X is C1-6alkylene or 1,4-piperidyl;        Y is absent, O, CONH or —C≡C—;        R1 is H, CN, N3, NH2, H2N—C(═NH), or H2N—C(═NH)—NH, where the primary amino groups can also be provided with conventional amino protective groups;        R2 and R3 are independently H, A, A—SO2—, Ar—SO2—, camphor-10-SO2—, COOA or a conventional amino protective group;        A and R4 are independently H, C1-10alkyl, or benzyl; and        Ar is phenyl or benzyl, each of which is unsubstituted or monosubstituted by CH3;        and their physiologically acceptable salts.        
The disclosed compounds are described as αv-integrin antagonists (especially αvβ3 antagonists) useful in the treatment of tumors, osteoporoses, and osteolytic disorders and for suppressing angiogenesis.
PCT Published Application WO 98/00395, published Jan. 8, 1998, discloses novel tyrosine and phenylalanine derivatives as αv integrin and GPIIb/IIIa antagonists having the general formula: wherein                X can be, among other groups, alkyl, aryl or cycloalkyl;        Y and Z can be alkyl, O, S, NH, C(═O), CONH, NHCO, C(═S), SO2NH, NHSO2, CA═CA′ or —C≡C—;        R1 can be H2N—C(═NH) or H2N—(C═NH)—NH;        R2 is A, aryl or aralkyl;        R3 is hydrogen or A;        R4 is hydrogen, halogen, OA, NHA, NAA′, —NH-Acyl, —O-Acyl, CN, NO2, SA, SOA, SO2A, SO2Ar or SO3H; and        A and A′ can be hydrogen, alkyl or cycloalkyl.        
The publication discloses the use of the compounds in pharmaceutical preparations for the treatment of thrombosis, infarction, coronary heart disease, tumors, arteriosclerosis, infection and inflammation.
A need continues to exist for non-peptide compounds that are potent and selective integrin antagonists, and which possess greater bioavailability or fewer side-effects than currently available integrin antagonists.